This Resource Letter provides a guide to the literature on the internally generatedgeomagnetic field. The topics covered include the origin of the geomagnetic field and the energy requirements and core properties necessary for its generation; a description of the geomagnetic field, including its spherical harmonic representation, and its rates of change, as well as models of the secular variation; observations of the field relevant to paleomagnetism and continental drift; information about magnetic anomalies in the oceans, sea floor spreading and plate tectonics; reversals of the geomagnetic field and magnetochronology.

We built a simple alternating voltage battery that periodically reverses value and sign of its electromotive force (emf). This battery consists of two coupled concentration salt-water oscillators that are phase shifted by initially extracting some drops of salt solution from one of the two oscillators. Although the actual frequency (period: ∼30 s) and emf (∼±55 mV) is low, our battery is suitable to demonstrate a practical application of oscillating systems in the physical, chemical, or biological laboratory for undergraduates. Interpretation of the phenomenon is given.

Two fluid devices exhibit simple aspects of nonlinear finite-amplitude instability in laminar fluid flow. The first shows multiequilibria; two steady flow regimes can be found within a certain range of the control parameter. The flow exhibits hysteresis as the control parameter is slowly increased and then decreased through this range of the control parameter. The second shows transition from steady flow to finite amplitude oscillations within a certain range. The two experiments share similar dynamics and only use different control parameters. A third experiment is described that exhibits either multiequilibria or oscillations, depending on which variable is selected to be the control parameter.

The spin–orbit interaction and Thomas precession calculation is almost always done in the electron’s rest frame. We show here that the alternative use of the lab frame is interesting in its own right, both because naive expectations fail and because it requires the presence of a “hidden momentum” contribution.

We extend the classical dielectricimage problem for an external point charge interacting with a semi-infinite medium to the case of an anisotropicdielectric. We show that the exterior potential is a solution to an unconventional image problem. By contrast the interior potential is not a solution to any simple image system; instead it can be obtained through an anamorphic transformation of an image solution. We calculate the volume bound charge density that is induced within the anisotropicdielectric and distinguishes it from an isotropic medium where the volume density vanishes. This solution provides a very simple and physically relevant example in which the physics of the surface and volume bound charge densities in a polarized dielectric can be analyzed.

The impact between a clubhead and a golf ball along with the resulting flight and run of the ball after landing is considered. The clubhead loft which results in the maximum drive distance and its dependence on the initial clubhead speed is then determined.

Special relativity is reformulated as a symmetry property of space-time:space-time exchange invariance. The additional hypothesis of spatial homogeneity is then sufficient to derive the Lorentz transformation without reference to the traditional form of the Principle of Special Relativity. The kinematical version of the latter is shown to be a consequence of the Lorentz transformation. As a dynamical application, the laws of electrodynamics and magnetodynamics are derived from those of electrostatics and magnetostatics respectively. The four-vector nature of the electromagnetic potential plays a crucial role in the last two derivations.

During a 10-day course in astronomy and particle physics, two research classes with 17–18 year old secondary school students studied the differential rotation of the milky way, the intricacies of high energy particle collisions and learned about the origin of the universe. The combination of making their own measurements of the milky way with a small radio telescope, using scientific data from high energy particle collisions, and having the big bang explained by scientists created an attractive and fascinating course in contemporary science.

We demonstrate a spatial Fourier filtering experiment that goes beyond the conventional low- and high-pass filtering and is not described in the Fourier optics books. Blocking nearly all the light in the Fourier plane of a 4-f filtering system is shown to produce at the output plane an image that is substantially different from the one corresponding to high-pass filtering. It is verified that the presented effect is due to the very high spatial frequency components created by the film emulsion scattering. This experiment can be performed in any undergraduate level optics laboratory with the same setup normally used for the Fourier filtering.

A simple model of eddycurrents in which current is computed solely from magnetic forces acting on electrons proves accessible to introductory students and gives a good qualitative account of eddycurrent forces. However, this model cannot be complete; it ignores the electric fields that drive current outside regions of significant magnetic field. In this paper we show how to extend the model to obtain a boundary value problem for current density. Solution of this problem in polar coordinates shows that the electric field significantly affects the quantitative results and presents an exercise suitable for upper division students. We apply elliptic cylindrical coordinates to generalize the result and offer an exercise useful for teaching graduate students how to use nonstandard coordinate systems.

We describe the implementation of a new laboratory-based interdisciplinary undergraduate course on nonlinear dynamical systems.Geometrical methods and data visualization techniques are especially emphasized. A novel feature of the course is a required laboratory where the students analyze the behavior of a number of dynamical systems. Most of the laboratory experiments can be economically implemented using equipment available in many introductory physics microcomputer-based laboratories.

In a hillingarmirage, the Earth’s surface appears flat, because nearly horizontal light rays have the same curvature as the Earth. A linear temperature profile is traditionally inferred; its gradient is calculated to give this curvature to the exact horizontal ray. To see an image, however, a bundle of rays is required. To ensure that each ray in the bundle have the same curvature, the temperature profile must contain a small positive quadratic term, the coefficient of which is derived.